Are you sure they are bees? Bees make temporary homes on trees, foliage, houses etc. during a phenomenon called "swarming". But that is only a temporary refuge until they find a more permanent home. In your case I suspect it is wasps or yellow jackets. During swarming, bees clump together for up to 24 hours at their temporary home.

aluvaboy, all that is only true of honey bees. There are many other kinds of bees; most are solitary. Stripes, can you take a photo of the insects in your pot?

Yes I agree. I know only two kinds of bees. Honey bees & bumble bees. Bumble bees usually nest in the ground. You are right - a photo should help.